I\'m creating a multiplayer game(based in websockets) which runs directly from t

Question

I'm creating a multiplayer game(based in websockets) which runs directly from the browser and which has multiplayer functionality. Each player needs to have his own account(Username and password). When I was planning the game, I realized that the easiest way to migrate it to other platforms is writing it in HTML5. So, I need to create a login system using JS and websockets. But I'm not sure of how secure is to send a message with a content like username and password to the websocket server(which runs in a Java virtual machine).
What's the best way to authenticate an user using a websocket?

Explanation / Answer

If you want security, transmitting authentication data through TLS is a big start. But let's assume the websocket is already set up over TLS. A solution I would recommend would be based on a challenge-response mecanism :

1. The server would set up a random set of bytes (the challenge), set a timeout at the end of which the challenge wouldn't be authorized.
2. The client would send in "plain text" the username and the challenge and an hash (with a SHA2 or SHA3 algorithm) of challenge || username || f(password), f(password) being how the password is stored in the database (a SHA256 of password for instance
3. The server verifies with the username's data and the challenge the response and if so, authenticates the user. It also invalidates the challenge to invalidate any future attempt using this challenge

This method provides an anti-replay fonctionnality : an attacker could not capure the data and replay it later to authenticate.

I however have one big problem with this method : f(password) has here the roughly same security as password : if the database leaks, any attacker could authenticate as anybody else. I say "roughly" because, if stored in clear text, since a lot of users are using the same password on multiple websites (which is bad), their accounts could be compromised elsewhere.

I can't think of a method protecting against a database leakage and an anti-replay mechanism, but an anti-database leakage mechanism (send user password in clear text over TLS, hash password with database salt and compare with database) over TLS should be sufficient enough against most risks you will face

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